Headward erosion of knickpoints in stream channels and spillways represents a risk to the safety of dams and other riverine structures. Knickpoint erosion is often initiated at a geometric anomaly in the channel profile, be it man-made or natural. Rock strength properties, stratigraphic relationships and structure are all controlling geological factors in the phenomena of knickpoint erosion. Hydrodynamic factors are controlled by the relationship between the depth of water and height of fall and whether the flow system is vented or not. At high flow volumes compared to the height of the fall, the knickpoint acts as a minor irregularity on the channel floor and retreat is minimized. However, at low flows, unvented conditions can develop over the knickpoint and significant amounts of erosion and headward cutting are possible. A knowledge of the phenomena of knickpoint erosion is critical to the safe design and operation of riverine structures.

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